Chemical insecticides are used to control insects that damage agricultural commodities such as grapes, cotton, barley, citrus, pecans, Christmas trees, etc. However, recent concerns about insecticide residues on commodities, resistance of insects to chemical insecticides, hazardous exposure to pesticide applicators, environmental contamination, destruction of natural biocontrol agents, such as beneficial insects, and lack of newly developed insecticides have increased the need for alternative control methods. Furthermore, as pests become more resistant to pesticides, more frequent treatments are required which increases the human health hazard.
An alternative to chemical pesticides is the use of biocontrol agents such as beneficial or predaceous insects which eat harmful insects. To date, there is no practical or adequate way to deliver known quantities of predaceous insects to pest infested plants. Eggs are usually applied to plants by shaking them from a container onto the plant foliage. A large percent of the eggs fall to the ground and are quickly destroyed by ants and other predators. Larvae that emerge from the fallen eggs which escape predators are usually unable to find their way back up the plant and starve to death and the infesting insect on the plant continues to do damage. Some lacewing producers sell larvae from hatched eggs which are then shaken onto plants. However, this too is very inefficient since lacewings are cannibalistic, and when confined to a container consume each other. Furthermore, when larvae are shaken onto plants, like the unhatched eggs, most of the larvae fall to the ground and are destroyed by ants or starve to death. One prior art method (Dreistadt et al, Entomophaga, Volume 31(4), pp. 397-400, 1986), discloses the use paper strips with thin lines of rubber cement for attaching lacewing eggs for placement in trees. The paper tapes are prepared manually and attached to trees manually. The disclosed process takes several days since the rubber cement has to dry for several days prior to attachment of the eggs in order to eliminate toxic solvents. Upon hatching, larvae tend to become entangled by the tacky rubber cement and die. There are various types of prior art devices for attaching and delivering beneficial insect eggs to agricultural commodities. For example, U.S. Pat. No. 3,847,113 ('113) discloses a device which pastes insect eggs on a substratum. The '113 device is not designed for field use and requires several additional labor intensive acts. Eggs of a host insect are applied in a single layer to paper and excess eggs are vibrated or scraped off. The layer of host insect eggs on paper is then exposed to a parasitic wasp such as Trichogramma spp. in a separate cage where the eggs are parasitized by the Trichogramma. The excess eggs, which would have been vibrated or scraped off, would necessarily have to be manually recycled into egg loading 1 bin of '113. In order to apply eggs of other beneficial insects, such as lacewing eggs which are 25 times larger than the host egg used in '113, it would be necessary to use large amounts of filler in order to distribute only a few eggs onto the glued surface in order to prevent cannibalism once the eggs hatch. Furthermore, the device disclosed in '113 does not separate the paper with eggs into narrow strips which could be distributed over long distances but instead separates the paper into squares that are manually attached to plants. If long lengths of narrow paper were prepared, it would require manual preparation of the strips and some method of attachment to plants at frequent intervals. In transporting tape paper with eggs to the field and in applying them to plants several problems must be dealt with, such as the wind, overheating of eggs in the carrying container, injury and dislodgement of eggs when large volumes are transported in containers, and the requirement of intensive labor for applying individual strips at each site or to each plant. Finally, the '113 device only operates at one speed and is regulated by the slit size in the bottom of egg bin and by vibrator 3.
U.S. Pat. No. 4,260,108 discloses a device for airborne release and broadcast of loose insect eggs. The disadvantages of this technique are similar to the disadvantages of the manual distribution of eggs discussed above i.e., the eggs do not necessarily fall onto the plants.
While various devices have been developed for the delivery of beneficial insect eggs to agricultural commodities, there still remains a need in the art for a more effective device for economically applying large quantities of predaceous insects, with equal distribution, to pest infested plants. The present invention provides a simple, cost effective, alternative strategy for delivering eggs of any predaceous insect which is different from the prior art devices and solves some of the problems associated with the prior art devices.